Colton Harvey of Ozark leaves the Pope County Courthouse in Russellville on Wednesday, June 6, 2012. The 15-year-old, charged as an adult with shooting his older sister three times in the head in January as she slept at their rural Arkansas home, pleaded guilty Wednesday to second-degree murder in exchange for a 45-year prison term. (THE COURIER / Joshua Mashon)

LITTLE ROCK (AP) — An Arkansas teenager who admitted shooting and killing his sister as she slept never told police or prosecutors why he did it, but according to a childhood friend, the 15-year-old hated the straight-A student and athlete.

That friend described animosity between Colton Harvey and his 16-year-old sister, Candace, in an interview with authorities obtained Thursday by The Associated Press under a Freedom of Information Act request. Harvey pleaded guilty to second-degree murder this week in exchange for a 45-year prison sentence.

“He’s always said that he hated his sister, but he wasn’t ever saying nothing about he was gonna kill his sister,” the friend said in February, about a month after Harvey pointed his father’s rifle at his sister’s head and fired three shots.

Harvey turned himself in the morning of the shooting, after heading to that friend’s home and telling him what happened.

Harvey never explained to authorities or the court why he killed his sister. While his friend’s answers hint at one possible explanation, his mother, in another interview with authorities, said her children didn’t really fight.

“If he tries to start something, Candace will just go to her room and shut the door,” Erica Harvey said the day of the shooting, according to a state police report. “When we leave them at home alone, Colton tries to be in charge and he will take over the remote to the TV and stuff and so Candace will just go to her room.”

Candace played basketball and did well in school. Her brother used to play football, his mother told an investigator, but his parents pulled him out when his grades fell.

The two teens had hardly seen each other the weekend Candace died, their mom told state police. Candace had a ballgame and work. Her brother, meanwhile, picked up rocks as punishment and stewed in his room after his parents grounded him for using chewing tobacco.

Then, on Jan. 15, the Harveys woke their son up to tend to some jerky from the deer he had shot the weekend before. While Erica Harvey and her husband were grocery shopping, Colton Harvey grabbed his father’s gun and pointed the barrel at his sister’s forehead and fired. She awoke with a scream, and he shot her in the head twice more.

“I think that he just wanted to hurt me and his father and he knew this would kill us,” their mother said, according to the state police report.

After the shooting, Harvey climbed in his father’s truck and took off with a bag of clothes, ammunition and deodorant. He started driving toward the hills, then changed his mind and headed to the sheriff’s office. He was scared, so he left and went to his friend’s house for some chewing tobacco. He confessed to his friend before returning to the sheriff’s office.

Harvey’s friend, whom the AP isn’t identifying because he is underage and would have likely been a witness had the case gone to trial, said he didn’t believe Harvey when he told him he shot his sister.

“I thought he was just messing with me,” the friend said in the interview with authorities.

Investigators found Candace’s body in the family’s home near Ozark, a town of about 3,600 roughly 120 miles northwest of Little Rock.

Prosecutors initially charged Harvey with first-degree murder, which carries a maximum penalty of life without parole, but they later worked out a plea bargain with his attorney.

That lawyer, Bill James, said there is a history of mental illness in Harvey’s family, but he said an expert wasn’t able to give his client a diagnosis because of his young age.

A state review of Harvey’s mental health noted he was depressed after being jailed and that he said he had lost consciousness playing football in junior high school. But it found nothing on which to blame the shooting.

Harvey’s attorney said there was some sibling rivalry, but nothing that could have foreshadowed what happened.

Harvey’s friend said Candace snitched on her brother even though he kept his mouth shut. He described Candace as the “golden child” who got whatever she wanted, while Harvey “just got kicked off to the side.”

“I guess he finally got tired of it one day and went off,” the friend said.